This invention relates to sluice gates for isolating the flow of liquids through sluice openings. In a conventionally designed sluice gate a sliding gate or plate is arranged to cover or uncover the sluice opening. When the opening is closed the pressure of the liquid being isolated is active on the area of the gate covering the opening and causes friction in opposition to opening or closing movement between the gate and the frame against which it seals. In a rigid gate assembly it is also necessary for the gate and the frame against which it seals to be accurately machined to preclude leakage. Because the opening and closing movement is a sliding movement and also because the gate has to be strong enough to withstand the differential pressure on closure it is not easy to incorporate resilient sealing faces.